None.
The present invention relates generally to the field of magnetic data storage and retrieval systems. More particularly, the present invention relates to a magnetoresistive read sensor having a magnetoresistive element, a pair of overlaid leads and a current guiding layer for directing substantially all of bias current through a narrow region close to an active central area of the magnetoresistive element.
A transducing head of a magnetic data storage and retrieval system typically includes a magnetoresistive (MR) reader portion for retrieving magnetic data stored on a magnetic media. The reader is typically formed of several layers which include a MR sensor positioned between two gap layers, which are in turn positioned between two shield layers. The MR sensor may be any one of a plurality of MR-type sensors, including, but not limited to, AMR, GMR, spin valve and spin tunneling sensors.
To operate the MR sensor properly, the sensor must be stabilized against the formation of edge domains because domain wall motion results in electrical noise that makes data recovery impossible. A common way to achieve stabilization is with a permanent magnet abutted junction design. Permanent magnets have a high coercive field (i.e., are hard magnets). The magnetostatic field from the permanent magnets stabilizes the MR sensor and prevents edge domain formation, and provides proper bias.
Tabs of antiferromagnetic material, sometimes called xe2x80x9cexchange tabs,xe2x80x9d have also been used to stabilize the MR sensor. Exchange tabs are deposited upon the outer regions of the MR sensor and are exchange coupled thereto. Functions of the exchange tabs include pinning the magnetization of the outer regions of the MR sensor in the proper direction, preventing the formation of edge domains and defining the width of an active area of the MR sensor by preventing rotation of the magnetization at of the outer regions of MR sensor.
When the transducing head is placed near a magnetic medium, a resistance of the MR sensor fluctuates in response to a magnetic field emanating from written transitions in the magnetic medium. By providing a sense current through the MR sensor, the resistance of the sensor can be measured and used by external circuitry to decipher the information stored on the magnetic medium. The sense current is provided to the MR sensor via a pair of current contacts.
In prior art transducing heads, the current contacts were deposited on the biasing elements (either the abutted junction permanent magnets or the exchange tabs), such that the sense current passes through the MR sensor via the biasing elements. This arrangement of current contacts and biasing elements in prior art transducing heads allows for the sense current and the magnetic bias to share a common path through the biasing elements. It was previously believed that a shared magnetic and electrical path would occupy less physical space to allow for a smaller transducing head to be built. However, to be electrically reliable, the interface between the biasing elements and the MR sensor needs to be large in surface area to minimize the electrical resistance and to minimize the possibility of open contacts caused by the manufacturing process.
More recently, the use of overlaid current contacts have been used. As with the traditional current contact configurations, the pair of overlaid current contacts are deposited upon the biasing elements. However, the overlaid current contacts differ from the traditional current contacts in that the overlaid current contacts are also deposited directly on portions of the MR sensor. To ensure that most of the sense current flows directly into the MR sensor, rather than passing first through the biasing elements, the relative conductivities of the overlaid current contacts, the MR sensor, and the biasing elements can be controlled. Nonetheless, some of the sense current will still pass through the biasing elements before entering the MR sensor, contributing to side-reading in intermediate areas of the MR sensor in which the bias field exerted by the biasing elements has dropped off.
Accordingly, there is a need for a means of forcing the sense current through the active regions of the MR sensor.
The present invention is a magnetoresistive sensor having overlaid leads and an insulating current guide layer for preventing diversion of current through the biasing means.
A magnetoresistive read sensor has a magnetoresistive element, first and second bias elements, first and second current guides, and first and second overlaid leads. The magnetoresistive element has a center region and end regions separated by the center region. The first and second bias elements are positioned on the end regions of the magnetoresistive element. The first and second current guides are positioned on respective first and second bias elements. Each of the first and second current guides extends a guide overlay distance onto the center region of magnetoresistive element. The first and second overlaid leads are positioned on respective first and second current guides. Each of the first and second overlaid leads extends a lead-insulator offset distance onto the center region of the magnetoresistive element. The first and second overlaid leads are separated by a lead separation distance.